King Charles's grandfather, King George VI, wrote in his diary on June 6 1944: "The news was given out at 8am that the invasion of the continent of Europe had started last night."
"The airborne troops had made successful landings in the night and had captured their objectives. So that was something".
This week, His Majesty revealed his grandfather's frustration of not being allowed to immediately travel to Normandy on D-Day.
He told veterans at Buckingham Palace recently that they [the British Government] wouldn't let him go for "several days".
Prince William followed the late Queen's example when filling in for King Charles.
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The site of veterans close to 100 years old, determined to stand up from their wheelchairs when The King and Queen arrived at the Royal British Legion's commemorative event at the British Normandy Memorial, indicates their respect for the family whose patriarch is Head of the British Armed forces.
These brave veterans, who stormed the beaches of Normandy facing the wrath of Nazi machine guns, belong to the generation of the late Queen Elizabeth II.
The young Princess Elizabeth was evacuated with her sister, Princess Margaret, to Windsor Castle during the war - delivering her first live broadcast to the nation to comfort fellow evacuees escaping German bombers.
The young Princess also joined the Auxiliary Territorial Service, the women's branch of the British Army, in the latter stages of the Second World War.
King George VI and Queen Elizabeth (The Queen Mother) stayed in London to boost morale.
When Buckingham Palace was bombed during the London Blitz, The Queen Mother famously said she could "finally look the East End in the eye", the area of Britain's capital city that endured particularly heavy bombardment in 1940-41.
The Royal Family, arguably, had a much more important role in contributing to the success of D-Day rather than simply boosting morale.
According to reports, the British Government used the Royal Family to try and trick the Germans into thinking the Allied invasion of France would happen in Calais or Scandinavia, rather than Normandy.
King George VI was sent to the South East of England and the Orkney Islands to visit troops in an attempt to deceive the enemy.
King Charles's mother and grandfather's contribution to the war effort undoubtedly ran through the King's mind over the last few days.
His Majesty was visibly moved to hear the testimony of four D-Day veterans at Buckingham Palace this week alongside The Queen.
Arthur Orborne (100), John Dennett (99), Bernard Morgan (100) and Jim Miller (100) were invited to Buckingham Palace to spend time with the King and Queen.
His Majesty showed the veterans a photograph of his grandfather, King George VI, on the beaches of Normandy several days after D-Day when the front line had moved further into France.
In Portsmouth yesterday, The Queen was reduced to tears by the moving commemoration ceremony involving several veterans.
Her own father, Major Bruce Shand, was injured fighting in Egypt during the Second World War - so the sacrifice and loss of the wartime generation was particularly poignant for her.
In Portsmouth yesterday, The Queen was reduced to tears by the moving commemoration ceremony involving several veterans.
GettyDespite his cancer diagnosis, the King was determined to honour the sacrifices of D-Day veterans and had managed to attend events in both Portsmouth and Normandy.
On doctors' advice, he has conceded that attending the International commemorative ceremony at Omaha Beach alongside more than 25 other Heads of State would have been one step too far.
It is understood His Majesty has other commitments on the day but was delighted his son, the Prince of Wales, represented him and the United Kingdom at the event.
It is thought to be the first time Prince William had officially stood in for his father at an international event since the King started his cancer treatment, giving us a glimpse into the distant future.
It is understood His Majesty has other commitments on the day but was delighted his son, the Prince of Wales, represented him and the United Kingdom at the event.
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Yesterday, Prince William joined the King and Queen in commemorations in Portsmouth but showed no visible signs of emotion - something his grandmother, Queen Elizabeth II, rarely showed.
Is this a sign Prince William is taking more after his beloved grandmother?
In normal times, the Princess of Wales would have accompanied her husband to the important international commemorations, but her ongoing recovery meant she couldn't attend.
Earlier today, the prince delivered a speech at the Canadian commemorative ceremony where he honoured the "bravery and sacrifice of Canadian troops".
Prince William also met army cadets and other Canadian youth representatives - citizens who will one day call William King of Canada.
Today, however, is all about honouring the veterans of the Normandy Landings.
The few who are left will likely no longer be with us for the 90th anniversary in 2034, but it is understood British officials want to ensure the "inspiring message of D-Day" passes to the next generation.
One day, it will be up to Prince George to lead the Royal Family in commemorating Armed Forces veterans, ensuring the fight for our freedom is never forgotten.
